We have exchange 2016. we facing issue in outlook. showing confirm your phone number in outlook. if we close this windows showing need password. we are facing for most of the users. how we can resolved this issue.

We have exchange 2016. we facing issue in outlook. showing confirm your phone number in outlook. if we close this windows showing need password. we are facing for most of the users. how we can resolved this issue.

What version of Outlook are you using? From your screenshot it seems to be Outlook 2016.
You can check the version and the build number via File > Office Account > About Outlook.
If you are using Outlook 2016 version 16.0.6741.2017 or some later versions, the issue may be caused by Outlook trying to connect to Microsoft 365.
To confirm it, you may run a Test E-mail Autoconfiguration via the Outlook client and check the results under the log tag to see if autodiscover is working properly.
If it is the cause of the issue, you may need to:
1.open registry on client device
2.locate HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Outlook\AutoDiscover
3.add a DWORD value named "ExcludeExplicitO365Endpoint" and set its value to 1
4.restart Outlook and see if the problem persists
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Already we have created this registry value but no luck. we have configure profile in another device where outlook version is 2019 but same issue. User maybe face this issue when they connected from external network.
Thanks for the information.
Have you run the Test E-mail Autoconfiguration via Outlook?
If possible, please post a screenshot of the result.
(And don't forget to hide your personal information)
Sorry I need to ask some more questions:
Have you activated Outlook (Office) using the Microsoft account?
If so, if you enter the phone number of the Microsoft account, will it get rid of the pop-up?
Or you may also skip the activation to test and see if Outlook can connect successfully.
I think the issue may have something to do with Microsoft account verification.
I am writing here to confirm with you how thing going now?
Did the issue get resolved?
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